Heliostats may now trap half the energy from sunlight and convert it into electrical and heat energy
a heliostat is being developed that increases the output of photovoltaic (pv) modules by more than 450 per cent. Colin Johnson and his colleagues at HelioEnergy of Whangarei, New Zealand, have designed the machine that uses a clockwork mechanism to turn a mirror to focus the Sun's light in fixed direction and thus obtain the solar energy. The device has been fitted with flat strips of ordinary glass mirror, which is used to reflect the Sun's light onto photovoltaic modules (Solar Progress , Vol 18, No 3).
A fraction of electricity generated during this process is used by the machine itself to run the self-regulating tracking apparatus. Although the solar energy is used separately by other devices as light or heat (thermal), the designing of the heliostat has been done in such a way that it can use both forms of energy in one machine.
The system can be used to heat swimming pools, in water desalination and purification as well as water heating for clinics and similar facilities. The researchers say that the machine can convert more than 50 per cent of the energy of full sunlight into a combination of electrical and heat energy.
The device is made up of simple materials that makes it accessible to many. It can also be manufactured at a mass scale. Other features of the device is that it is easy to assemble and transport it. So it can be a realistic energy source for disaster relief and in remote areas where electrification is difficult. The energy produced by the machine can enable it to pump 10,000 litres of water per hour.
Theoretically, it is possible for the machine to produce nearly 960 watts of electricity with the help of ten slightly modified pv modules. Johnson says, the heliostat could be able to generate a minimum electrical output of 700 watts. During trials, the prototype produced nearly 360 watts of electricity on a winter's day at Whangarei. Studies have shown that the system automatically locates and track the sunlight with efficient accuracy to obtain its maximum electrical output capability.
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